Cassette invertor method

ABSTRACT

A method of inverting a plurality of plate-like materials. One form of the method may include supporting the plurality of plate-like materials in an orientation such that the plate-like materials are substantially parallel to each other in a first orientation. The method may also include engaging portions of each plate-like material to retain the plate-like materials in the substantially parallel orientation to each other, and simultaneously inverting the plate-like material to a second orientation.

This is a divisional application of U.S. patent application Ser. No.09/130,262, filed Aug. 6, 1998, and issued as U.S. Pat. No. 6,254,682 onJul. 3, 2001 and which is a continuation of U.S. patent application Ser.No. 08/603,879, filed on Feb. 22, 1996, and issued as U.S. Pat. No.5,858,459 on Jan. 12, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to manipulation of bulk quantities ofplate-like material. More particularly, the present invention relates toinverting a plurality of flat panel substrates and the like contained ina cassette-type carrier.

2. Description of the Invention Background

Many advances in the fields of electronics and optics, as well as otherfields, have resulted from the development of multilayered plate-likedevices, such as flat panel displays, optical devices, printed circuitboards and integrated circuits, that provide for more efficientperformance of sequential operations. The performance characteristics ofthe multi-layered devices are precisely determined by the composition,the dimensions and the surface characteristics of the individual layers.In the electronics industry, the desire for faster operating speeds andincreased storage capacities have motivated advances in theminiaturization of components that has placed increasing demands on thecapabilities of electronics manufacturers. In response to those demands,manufacturers have developed new techniques that are directed towardmeeting the increased expectations of the industry.

One way to reduce the size of the device is to produce the deviceshaving thinner layers thereby reducing the profile of the devices. Areduction in thickness can be realized especially for those layers inwhich the performance of the device is not dependent on the thickness ofthe layer, but merely depends on the presence of the layer, such as withinsulating layers and the like. An equally strong motivation to producethinner coating layers is that the coating materials, in many instances,are relatively expensive; therefore, a reduction in the thickness of thelayers directly reduces the manufacturing cost of the device.

The most common method of coating the surface involves dipping thedevice into the coating material. This method, while providing for fullcoverage of the device does not produce consistent nor predictablecoating thickness due to inherent slight variations in the coatingproperties and the numerous process conditions.

An alternative technique developed to produce coating layers that arethinner than normally achievable by dipping is to spin coat the materialonto the substrate. In spin coating methods, a coating is applied to thesurface of the substrate and then the substrate is spun at asufficiently high rate, such that the rotational force developed by thespinning motion will cause the coating material to distribute over thesurface of the substrate and a portion of the coating material will bespun off the substrate depending upon the strength of the rotationalforce. A problem with this method is that a significant amount ofcoating material is wasted, which increases overall production costs ofthe devices. In addition, the method may not provide a uniform thicknesslayer if the topography of the substrate is sufficiently rough, becausethe raised portions of the surface will tend to retain coating materialthat would otherwise have been spun off, thereby resulting in localizedthickness variations.

A current preferred technique to produce thin coating layers involvesperforming a meniscus coating of the surface, as is disclosed in U.S.Pat. Nos. 4,370,356 and 5,270,079 to Bok. In the meniscus coatingprocess, the surface of a substrate to be coated is oriented downwardand the substrate is moved relative to a coating applicator such thatthe bottom surface is brought into sufficiently close proximity to thecoating applicator so as contact the coating material flowing from theapplicator. The coating material forms a meniscus on the surface of thesubstrate that forms a uniform thin layer of the bottom surface as thesubstrate is moved relative to the applicator. The coating thickness iscontrolled by the distance between the applicator and the substratesurface and the flow of coating material through the applicator. Thistechnique is capable of producing uniform coatings with thicknesses ofless than a few microns. One inherent problem with this technique isthat the surface to be treated must be facing downward, whereas in mostother processes the surface to be treated must be facing upward and thattypically the handling of the substrates is performed using the bottomof the substrate.

In addition, some multilayered devices, such as those used in optics,are produced by depositing layers on both sides of a substrate. Thosetypes of devices presenting special handling and processing problemsbecause handling of either side of the plate-like material can damagethe layers affecting the performance of the device. The difficulty inhandling those materials results in increased production costs due tothe lower overall production yield. In addition, the increasedcomplexity and amount of equipment and floor space required to producethose devices and the resulting longer processing times also serves toincrease the production costs of devices that are coated on both sides.

Currently, plate-like materials that are to be treated using a meniscuscoating technique or other techniques involving treating the materialfrom below or on both sides can be handled in two ways. One method isdisclosed in U. S. Pat. No. 3,610,397 issued Oct. 5, 1971 to Bok (the“'397 patent”). In the practice of the '397 patent, individual plateshaving first and second sides are transported along a conveyor belt withthe second side of the plate in contact with the belt. The plates arepassed in successive fashion through processing stages in which thefirst side of the plate is treated from above the plate. In order toperform the meniscus coating of the first surface from beneath the plateor to coat the second side of the plate, the plate is flipped over usinga turnover device, so that the first side of the plate is in contactwith the belt. Following either meniscus coating of the first side orcoating of the second side, the plate must again be flipped over, usinga turnover device or some other appropriate method to return the plateto its original orientation.

A problem with conveyor-type apparatuses and methods is that additionalor more complex processors are required to handle the material. Thisresults in increased equipment costs and floor space requirements. Also,the '397 patent recognizes the problems associated with individuallyturning over each plate twice in the prior art; however, the patent onlydiscloses an apparatus intended to lessen the possibility of damage tothe plate through the use of less complex machinery to perform theflipping operations. Another problem in the prior art, not addressed bythe '397 patent, is when both sides of the material are to be treated,such as in optical applications, a freshly treated surfaces must bebrought into contact with handling equipment. The contact with thehandling equipment may damage the layers on the substrate and may alsorequire increased processing times to allow the freshly treated surfaceto dry or harden prior to handling the surface.

A second method is disclosed in U.S. Pat. No. 5,368,645 issued Nov. 29,1994 to Bok (the “'645 patent”) involves the use of a vacuum chuck toinvert the substrate or plate, thereby positioning the surface of theplate facing downward for treatment using the meniscus coatingtechnique. In the '645 patent, a plate with the surface to be treatedfacing upward is positioned on a rotatable vacuum chuck. A vacuum isdrawn through the chuck which holds the plate against the chuck and thechuck is rotated 180° so that the surface to be treated is facingdownward. The meniscus coating is applied to the plate and the vacuumchuck is returned to the upright position and the vacuum is released.

The use of vacuum chuck provides a solution to some of the problemsassociated with the prior art in that less additional equipment andfloor space is necessary; however, the use of the vacuum chuck stillrequires the plates to be individually inverted, and a vacuum to bedrawn and released, all of which increases the processing time and thepotential for damage to the plates presented by individual handling ofthe material. Additionally, the vacuum chuck apparatuses, like theconveyor belt apparatuses, are not suitable for handling material thatis to be treated on both sides.

The present invention is directed to providing a method and an apparatusfor efficiently inverting plate-like material in bulk which overcomes,among others, the above-discussed problems so as to minimize thehandling and processing equipment necessary to treat both sides of theplate-like material and to increase productivity and yield by minimizingdamage to the material resulting from material handling operations.

SUMMARY OF THE INVENTION

The above objects and others are accomplished by a cassette invertorapparatus and method in accordance with the present invention. Thecassette invertor apparatus of the present invention is provided forinverting plate-like material in bulk by securing the plate-likematerial in a cassette-type carrier, rotating both the cassette and theplate-like material and by moving the plate-like material between therail surfaces of the cassette in a restrained manner. The cassetteinvertor apparatus includes a base, a back attached to the base, a topthat is removably attachable to the back in a manner so as to secure acassette positioned between the top and the base and retractablematerial holders attached to the base for engaging and disengaging theplate-like material. In a preferred embodiment, the retractable materialholders are in the form of directly opposing retractable support blockshaving notches corresponding the edges of the plate-like material. Theblocks are reciprocally moved by a side actuator to enable the supportblocks to engage and disengage the plate-like material. Also in apreferred embodiment, support block actuators are attached to thesupport blocks to provide for restrained movement of the plate-likematerial between the surfaces of the cassette rails, and top actuatorsare provided to separate the top from the back of the apparatus. Inalternative embodiments, beveled notches in the support blocks are usedto provide restrained movement of the plate-like material between thesurfaces of the cassette rails.

Accordingly, the present invention provides effective solutions to theproblems present in the handling of plate-like materials that are to betreated using techniques that require the material to be inverted, suchas meniscus coating techniques, and also for materials that must betreated on both sides. As this invention provides an effective means forinverting plate-like material in bulk, the problems caused byindividually inverting each plate are eliminated. In addition, whenmaterials are to be treated on both sides, the present invention doesnot require that the first surface be placed in contact with thehandling equipment after processing and as a result the potential fordamage to the treated surface is greatly reduced. These and otherdetails, objects, and advantages of the invention will become apparentas the following detailed description of the present preferredembodiment thereof proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiment of the present invention will be described ingreater detail with reference to the accompanying drawings, wherein likemembers bear like reference numerals and wherein:

FIG. 1 is a front perspective partially exploded view of a preferredembodiment of the present invention with the top removed from theapparatus for clarity;

FIG. 2 is a front perspective view of a preferred embodiment of thepresent invention with an empty cassette in the apparatus; and,

FIG. 3 is a back perspective view of a preferred embodiment of thepresent invention showing the back of the apparatus and the sideactuator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The operation of the cassette invertor apparatus 10 will be describedgenerally with reference to the drawings for the purpose of illustratingpresent preferred embodiments of the invention only and not for purposesof limiting the same. The cassette invertor apparatus 10 of the presentinvention serves to invert a cassette 70 containing a plurality ofsheets of plate-like material 80 so that both sides of the plate-likematerial 80 can be treated using the same equipment, thereby reducingequipment redundancy and complexity and minimizing the floor spacerequired to perform the procedure. FIGS. 1, and 2, respectively, showone embodiment of the cassette invertor apparatus 10 without and with acassette 70 in place. While preferred embodiments of the invention willbe discussed with respect to inverting a plurality of flat panelscontained in a rectangular shaped cassette 70, one skilled in the artwill appreciate that the invention can be suitably modified for use withother plate-like material and carriers that may require treatment onboth sides of the material, such as semiconductor substrate wafers andthe like.

In a preferred embodiment, the cassette invertor apparatus 10 isprovided for a cassette 70 having two substantially open opposingsupport sides 78, and open front side 73, a substantially opensupporting back side 71, a top face 75 and a bottom face 77. Theplate-like materials 80 are seated on and supported by either the top orbase rail surfaces, 74 and 76, respectively, of the supporting rails 72depending upon the orientation of the apparatus 10.

The apparatus 10 includes a base 20, a back 50 attached to the base 20and a top 30 that is removably attached to the back 50 in a manner so asto be capable of securely holding the cassette 70 between the top 30 andthe base 20 without obstructing the open front side 73 of the cassette70. In a preferred embodiment the top 30, the base 20, and the back 50,are constructed of anodized aluminum; however, any material ofconstruction having sufficient strength to support the weight of theplate-like material 80 and the carrier 70 is acceptable.

The base 20 is substantially rectangularly shaped having base tabs 22extending from opposing sides 28, a back portion 21, a front portion 23,an inner surface 24 and an outer surface 26. The dimensions of the base20 from the front portion 23 to the back portion 21 are preferablysubstantially equivalent to the distance between the open front side 73and the back side 71 of the cassette 70. Preferably, the distancebetween opposing sides 28 is sufficiently larger than distance betweenopposing sides 78 of the cassette 70, to allow for attachment of movableside blocks 60 (described below) to the base 20. The base tabs 22 arecentered along the respective opposing sides 28 and are preferablysemicircular in shape and of a sufficient radius to allow a top actuator14 to be mounted on the inner surface 24.

Preferably, the back 50 is substantially rectangularly shaped and has atop portion 55, a bottom portion 57, an inner surface 54, an outersurface 56 and opposing sides 58 of substantially the same dimensions asthe distance between the opposing surfaces 28 of the base 20. Thedimensions of the back 50 from the bottom portion 57 to the top portion55 are preferably, substantially equivalent to the distance between thetop face 75 and the bottom face 77 of the cassette 70. The back 50 isattached at substantially a right angle to the back portion 21 of thebase 20. A pivot 51 is mounted to the outer surface 58 in the center ofthe back 50 to provide for rotation of the cassette invertor apparatus10 in the plane of the outer surface 56 of the back 50. Two cylindricalpost receivers 59 are attached to the top portion 55 of outer surface 56of the back 50 near respective opposing sides 58. The post receivers 59are axially oriented perpendicular to the base 20 and are used incombination with the guide posts 39 attached to the top 30 to guide thetop 30 into position relative to the back 50.

The top 30 is preferably substantially the same shape and dimensions asthe base 20, having tabs 32 extending from opposing sides 38, a backportion 31, a front portion 33, and an inner surface 34. The top 30 isattached to the back 50 by the top actuators 14 and through the use oftwo parallel mounted cylindrical guide posts 39 that are sized andpositioned to be received in the post receivers 59 on the back 50. Theguide posts 39 are attached to the back portion 31 of the top 30perpendicular to the inner surface 34, so that when the top 30 isattached to the back 50, the top 30 directly opposes the base 20. Thetop actuators 14 are attached to the underside of the top 30 and serveto raise the top 30 so apparatus 10 can receive a cassette 70 and top 30can be lowered to retain cassette 70 in apparatus 10. Other alternativeembodiments for securing the top 30 to the back 50, such as open andclose hinge arrangements, locking mechanisms, straps or using aremovable top 30 secured by a friction fit between guide posts 39 andpost receivers 59, are also contemplated in the practice of the presentinvention.

While a current preferred embodiment is for the base 20, the top 30 andthe back 50 to be solid members dimensionally comparable to thedimensions of the cassette 70, alternative embodiments, such as the useof frame-like members or members of differing sizes to support thecassette 70 may also be used with the present invention.

In a preferred embodiment, two top actuators 14 are mounted on the innersurface 24 of the respective base tabs 22 and attached to the respectivetop tabs 32 on opposing sides 28 of the base 20. The top actuators 14are used to raise and lower the top 30 with respect to the back 50. Thetop actuators 14 are preferably air actuated, such as those manufacturedby Bimba Corporation, Monee, Ill. 60449-0068. However, other typeactuators, such as hydraulic or mechanical, may be used with theinvention. In alternative embodiments, such as those using a lockingmechanism, the top actuator 14 may not be necessary to practice thepresent invention.

In a preferred embodiment, retractable material holders in the form ofnotched support blocks 40 are used to secure the plate-like material 80within the cassette 70, when the cassette 70 is being inverted.Preferably, two movable support blocks 40 are respectively positioned onopposing sides 28 of the base 20 so that the support blocks havedirectly opposing faces 46 containing directly corresponding horizontalnotches 44 of dimensions suitable for engaging the edges 86 of theplate-like material 80. The support blocks 40 are reciprocally movableto provide for the engagement and disengagement of the edges 86 of theplate-like material 80 in the notches 44 of the support blocks 40. Theportion of the faces 46 that directly oppose the support rails 72 of thecassette 70 are not notched and are also recessed to allow the notchedportion of the support blocks to be reciprocated through the openportions of the opposing sides 78 of the cassette 70 withoutinterference from the support rails 72. Two directly opposing supportblocks 40 with faces 46 having recessed unnotched portions are preferredto support the plate-like material 80, so as to eliminate any bendingmoment that may result from other support configurations, whileminimizing any potential for damage to the material 80 that may resultfrom additional contact with the apparatus 10. However, otherconfigurations and supports may be employed as necessary depending onthe type of carrier 70 used to hold the material 80 and the plate-likematerial 80 itself. The positioning of the support blocks 40 directlyfacing the opposing sides 78 of the cassette 70 is additionallypreferred so that the plate-like material 80 can be removed from thecassette 70 without having to remove the cassette 70 from the apparatus10. However, the present invention can be practiced using other supportblock 40 arrangements as may be necessary to accommodate other carrierdesigns, such as those designs that only provide sufficient access tothe edges 86 of the material 80 through the open front side 73, wherethe material 80 is placed into and taken out of the cassette 70.

Preferably, reciprocal movement of the support blocks 40 is provided bymounting the support blocks 40 to side blocks 60 slidably mounted onopposing sides 28 of the base 20. The slide blocks 60 are preferably “L”shaped and are slidably mounted in an inverted position with the innerhorizontal surface 61 contacting the inner surface 24 of the base 20.The vertical portions 65 of the side blocks 60 point toward and extendbeyond the outer surface 26 of the base 20. Two parallel guide rods 64are used to slidably connect the side blocks 60. The guide rods aresymmetrical about the center of the side blocks 60 and extend throughthe vertical portions 65 of the side blocks 60 below the outer surface26 of the base 20 and provide for reciprocal movement of the side blocks60 along the guide rods 64. Reciprocal movement of the support blocks 40is preferably provided by a side actuator 62 which is connected to oneside of a rotating hinge 66 mounted on the outer surface 26 in thecenter of the base 20. Actuator rods 68 are used to connect the sideblocks 60 to opposing sides of the rotating hinge 66. The actuation ofthe side actuator 62 imparts rotational motion to the rotating hinge 66.The rotation of the rotating hinge 66 moves the actuator rods 68 inopposite directions in a reciprocating fashion. The reciprocal movementof the actuator rods in opposite directions moves the side blocks 60either toward or away from each other depending on the direction of theactuation. The side actuator 62 is preferably air actuated, but otheractuators, such as hydraulic or mechanical, may be used with theinvention. The side actuator 62 used in such an arrangement provides forreciprocal movement of the side blocks 60 in opposite directions alongthe guide rods 64, thereby forcing the support blocks 40 into eitherengagement or disengagement with the edges 86 of the plate-like material80. While an actuator is a current preferred embodiment for producingreciprocal movement of the support blocks 40, any suitable method ofproducing reciprocal movement is considered acceptable.

In a preferred embodiment, support block actuators 42 are used toprovide for restrained movement of the plate-like material 80 from arest position on the base rail surface 74 when the apparatus 10 isoriented with the top 30 above the base 20 to a rest position on the toprail surface 76 when the cassette is inverted with the top 30 orientedbelow the base 20. The support blocks 40 are attached to the supportblock actuators 42, which are in turn mounted to the side blocks 60. Atotal of four support block actuators 42 are preferred with twoactuators 42 symmetrically attached to each support block 40 and mountedon the outer horizontal surface of the side blocks 60. The support blockactuators 42 are preferably air actuated, but other actuators, such ashydraulic or mechanical, may be used with the invention. Also, whileactuators are used in a current preferred embodiment for producingreciprocal movement of the support blocks 40, other apparatuses forproducing reciprocal movement, such as a friction slide, arecontemplated by the present invention. Alternatively, the edges of thenotches 44 can be beveled so that the dimension of the notches 44 at theface 46 of the support blocks 40 are substantially equal to the distancebetween the top and bottom rail surfaces 74 and 76, respectively, suchthat engagement and disengagement of the material 80 from the supportblocks 40 would provide restrained movement of the material between therespective rail surfaces, 74 and 76.

In the operation of the present invention. the top actuators 14 areextended to exert a force sufficient to separate the top 30 from theback 50. A cassette 70 containing plate-like material 80 seated on thebase rail surfaces 74 is positioned with the bottom face 77 of thecassette 70 contacting on the inner surface 24 of the base 20 betweenthe support blocks 40 and with opposing sides 78 directly opposingsupport blocks 40 and back side 71 contacting the inner surface 54 ofthe back 50. The top 30 is lowered onto the back 50 by retracting thetop actuators 14 and the cassette 70 is held between the top innersurface 34 and the base inner surface 24. The side actuator 62 isactuated to move the opposing side blocks 60 toward each other alongguide rods 64, thereby causing the opposing support blocks 40 to movetoward each other, and engage the edges 86 of the plate-like material 80which mate with and are retained in the notches 44 of the support blocks40. The cassette invertor apparatus 10 is then rotated 180° about thepivot 51 so that the top 30 and the base 20 have essentially exchangedpositions and the back 50 occupies essentially the same position but isoriented 180° out of phase from its original position. The blockactuators 42 are extended and the support blocks 40 are moved toward thetop 30 until the plate-like material 80 is in a close proximate relationwith base rail surface 76 of the cassette 70. The side actuator 62 isthen actuated to move apart the opposing support blocks 40 causing theedges 86 of the plate-like material 80 to disengage the notches 44 andthe plate-like material 80 seats on the base rail surface 76. In thecase of applying a meniscus coating, the plate-like material 80 is thenremoved from the cassette 70 and the first surface 82 is processed frombeneath the plate-like material 80 using a meniscus coating applicatorgraphically represented as 81 in FIG. 3 or any other bottom surfacetreatment technique as is known in the art, after which the plate-likematerial 80 is returned to the cassette 70. The side actuator 62 isagain actuated causing the support blocks 40 to move toward each other,and engage the edges 86 of the plate-like material 80 which mate withand are retained in notches 44 in the support blocks 40. The cassetteinvertor apparatus 10 is then rotated 180° about the pivot 51 and theapparatus 10 and cassette 70 are returned to their original positions.The block actuators 42 are actuated to move the support blocks 40 towardthe base 20 until the plate-like material is in a close proximaterelation with top rail surface 74 of the cassette 70. The side actuator62 is then actuated to move side blocks 60 and support blocks 40 apartcausing the edges 86 of the plate-like material 80 to disengage from thenotches 44 and the plate-like material 80 seats on the top rail surface74. The top actuators 14 are again extended to separate the top. 30 fromthe back 50. The cassette 70 containing the plate-like material 80 canthen be removed from the apparatus 10.

Those of ordinary skill in the art will appreciate that the presentinvention provides great advantages over the prior art for treatingplate-like materials using surface treatment techniques that requireapplication of a coating in a direction other than from above thematerial. Also, the subject invention eliminates the need to place afreshly treated surface in contact with other surfaces and is designedsuch that the same equipment can be used to process both sides of thematerial resulting in reduced equipment costs and other operating costssuch as those associated with reduced space requirements. In addition,the present invention can be integrated into a fully automatedprocedure, but is also suitable for manual handling of the plate-likematerial. Thus, the present invention provides a significant reductionin the overall cost associated with the production of plate-likematerial and a commensurate increase in the overall quality of thetreated material. While the subject invention provides these and otheradvantages over other apparatuses for handling plate-like material, itwill be understood, however, that various changes in the details,materials and arrangements of parts which have been herein described andillustrated in order to explain the nature of the invention may be madeby those skilled in the art within the principle and scope of theinvention as expressed in the appended claims.

What is claimed is:
 1. A method of inverting a plurality of plate-like materials, said method comprising: supporting the plurality of plate-like materials in an orientation such that the plate-like materials are substantially parallel to each other in a first orientation; engaging portions of each plate-like material to retain the plate-like materials in the substantially parallel orientation to each other; and simultaneously inverting the plate-like materials to a second orientation.
 2. The method of claim 1 wherein said engaging portions comprises engaging opposing edges of each plate-like material.
 3. The method of claim 1 wherein said simultaneously inverting comprises simultaneously rotating all of the plate-like materials about a pivot axis.
 4. A method of inverting a plurality of plate-like materials supported within a cassette, said method comprising: restraining each plate-like material within the cassette; and rotating the cassette about a pivot axis.
 5. The method of claim 4 wherein said restraining comprises engaging portions of each plate-like material.
 6. The method of claim 5 wherein said engaging portions comprises simultaneously engaging opposing edges of each plate-like material.
 7. A method of simultaneously inverting plate-like materials, said method comprising: forming a stack of plate-like materials; engaging portions of each plate-like material within the stack; and rotating the stack about a pivot axis.
 8. The method of claim 7 wherein said forming a stack comprises supporting each plate-like material in parallel relationship to each other.
 9. The method of claim 8 further comprising clamping the stack between two surfaces prior to said engaging.
 10. A method for applying a surface treatment to semiconductor wafers comprising: forming a stack of semiconductor wafers separately supported at their respective edges; retaining the semiconductor wafers within the stack; inverting the stack of semiconductor wafers; removing a semiconductor wafer from the stack; and applying a surface treatment to the semiconductor wafer. 